I am still using an old 310XT. I knew how to find lost or corrupted files when using Garmin ANT Agent, but am now using Garmin Express & can't find the lost activity.
Last week, I noticed the 310XT seems to be recording fine, but then after saving, was unable to see it in "history" on thwe unit, yet still was able to load & view the activities on Garmin Connect after syncing with Garmin Express. This weekend, I did 3 events, but now home & synced, only the last 2 are showing. Sadly, the missing activity is the one I'd really like to see, as the event also had a timing glitch & did not record my time! so was hoping to submit my data :(